1. Field of the Invention
The present invention relates to a device for measuring the earth's magnetic field disturbed by anomalies. More particularly, it leads to a device for measuring the earth's magnetic field and the anomalies thereof, from a land, sea or air carrying vehicle, which device includes an ultrasensitive magnetometric probe and means for compensating for the magnetic disturbances due to the carrying vehicle.
2. Description of the Prior Art
Certain devices already exist for measuring the earth's magnetic field and its anomalies.
Document No. FR-A-No. 2 060261 teaches such a device in which two magnetometric probes are mounted at the end of a mast. Besides the fact that it can only be used for single rotor helicopters, this device involves mounting the mast in the alignment of the shaft of the rotor, which results in operational constraints.
In other devices, a single magnetometric probe is used in cooperation with means for compensating for the disturbances of the magnetic field to be measured generated by the carrier vehicle. The magnetometric probe is moved as far away as possible from the carrier vehicle either at the end of a mast, fixed to the carrier vehicle, the compensation means being integrated in the carrier vehicle or, and for the case of aircraft, towed behind at the end of a cable.
Although these latter devices can be used on different types of carrier vehicles, the modifications of attitude of the carrier vehicle, that is to say the changes of orientation of the vehicle in the magnetic field to be measured, as well as the rate of these changes, however results in disturbances to the measurement.
Determination of this variable disturbing field, generated by the carrier vehicle, is obtained by a triaxial magnetometer which indicates the attitude of the carrier vehicle in the earth's magnetic field and by means of a gyrometric two axis block which indicates the rate of change of attitude of the carrier vehicle along two orthogonal axes.
Calculation of the compensation, using information delivered by said compensation means, requires previous harmonization of the magnetometric probe, of the magnetometer and of the gyrometric block, that is to say the paralleling of the reference trihedrons of these three sensors.
This operation is long, delicate, expensive and a hindrance from the operational point of view.